The invention relates to a communication network having a series architecture and comprising an electronic master device and a plurality of electronic slave devices interconnected by a common communication channel which terminates at a receiving port of the electronic master device, which common communication channel includes a first dedicated-line receiver upstream of the receiving port of the electronic master device to effect a voltage-level conversion in order to derive a relatively small voltage-level swing from a relatively large voltage-level swing applied to its input and apply said relatively small voltage-level swing to said receiving port of the electronic master device, each electronic slave device being provided with an associated connection device having a first input connected to a transmitting port of the relevant electronic slave device and an output connected to the common communication channel, which connection device is adapted to effect a voltage-level conversion from a relatively small voltage-level swing to a relatively large voltage-level swing.
Such communication networks are known and operate in accordance with well-defined standards such as European standard V 28 or United States Standard RS-232. The communication channel, which interconnects the various electronic devices, is unidirectional, i.e. it connects an electronic transmitting device to an electronic receiving device. It is obvious that satisfactory communication between two electronic devices may require the use of a plurality of connections in each direction and therefore it is customary to provide as many communication channels as necessary, each of the two electronic devices thus connected operating either as a transmitter or as a receiver for each channel.
It is also known to employ the master-slave architecture for a plurality of electronic devices, the electronic master device being capable of communicating with all the slaves but the slaves not being capable of communicating with each other.
When the slaves are remote from the master, their distance may be such that voltage-level conversions are necessary; in that case a star architecture could be employed, which presents no new technological problems, in contradistinction to a series architecture.
Indeed, the series architecture requires two types of connection, a first type enabling the electronic master device to operate as a transmitter for a plurality of electronic slave receiving devices and a second type enabling the electronic master device to function as a receiver for a plurality of possible electronic slave transmitting devices; the first type does not present any specific problems, in contradistinction to the second type. The receiving port of the electronic master device may operate at a voltage-level swing, of, for example 0.5 V (0 V=logic "0" level and 5 V=logic "1" level), whereas the distance between the various electronic devices may necessitate derivation of this voltage-level swing from a voltage-level swing of a higher absolute value, for example 12 V (="0") and -12 V (="1"). The required conversion may be effected by a dedicated-line receiver (for example that available under the type number 1489), the higher value voltage-level swing being applied to the communication channel by the outputs of the various connection devices. In such a case, the connection devices may themselves effect voltage-level swing conversion, this time from the lower voltage-level swing to the higher voltage-level swing, thereby enabling the transmitting port to operate at the higher voltage-level swing.
If the communication channel is in the form of a common line thereof in the rest condition, this common line may be, for example, at -12 V but during a transmission, the electronic slave transmitting device will attempt to pull the common line to +12 V by means of its connection device. This will give rise to an electrical short circuit with the other electronic slave devices which are not transmitting and which consequently maintain the common line at -12 V.